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BABAR_2011_I892421

Decay angles in $D_{s1}(2536)^+\to D^{*+}K^0$
Experiment: BABAR (PEP-II)
Inspire ID: 892421
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D83 (2011) 072003
Beams: e- e+
Beam energies: (5.3, 5.3) GeV
Run details:
  • e+e- to hadrons

Measurement of decay angles in the decay $D_{s1}(2536)^+\to D^{*+}K^0$ by BaBar.

Source code: BABAR_2011_I892421.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief D_s1 decay angles
  9  class BABAR_2011_I892421 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2011_I892421);
 14
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21      // projections
 22      declare(UnstableParticles(), "UFS");
 23      // book histos
 24      book(_h_cP,1,1,1);
 25      book(_h_c ,2,1,1);
 26    }
 27
 28    bool isK0(int id) {
 29      return id==310 || id==130 || abs(id)==311;
 30    }
 31
 32    /// Perform the per-event analysis
 33    void analyze(const Event& event) {
 34      static const int DsID = 10433;
 35      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 36      for (const Particle& p : ufs.particles(Cuts::abspid==DsID)) {
 37	// decay angle
 38	int sign = p.pid()/DsID;
 39	Particle Dstar;
 40	if(p.children().size()!=2) continue;
 41	if(p.children()[0].pid()==sign*413 &&
 42	   isK0(p.children()[1].pid())) {
 43	  Dstar = p.children()[0];
 44	}
 45	else if(p.children()[1].pid()==sign*413 &&
 46		isK0(p.children()[0].pid())) {
 47	  Dstar = p.children()[1];
 48	}
 49	else {
 50	  continue;
 51	}
 52	// first boost to the D_s1 rest frame
 53	LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
 54	FourMomentum pDstar = boost1.transform(Dstar.momentum());
 55	double cTheta = pDstar.p3().unit().dot(p.momentum().p3().unit());
 56	_h_c->fill(cTheta);
 57	if(Dstar.children().size()!=2) continue;
 58	Particle D0;
 59	if(Dstar.children()[0].pid()== sign*211 &&
 60	   Dstar.children()[1].pid()== sign*421) {
 61	  D0 = Dstar.children()[1];
 62	}
 63	else if(Dstar.children()[1].pid()== sign*211 &&
 64		Dstar.children()[0].pid()== sign*421) {
 65	  D0 = Dstar.children()[0];
 66	}
 67	else
 68	  continue;
 69	// boost to D_s frame
 70	FourMomentum pD  = boost1.transform(D0.momentum());
 71	// to D* rest frame
 72	LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDstar.betaVec());
 73	Vector3 axis = pDstar.p3().unit();
 74	FourMomentum pp = boost2.transform(pD);
 75	// calculate angle
 76	double cThetap = pp.p3().unit().dot(axis);
 77	_h_cP->fill(cThetap);
 78      }
 79    }
 80
 81
 82    /// Normalise histograms etc., after the run
 83    void finalize() {
 84      normalize(_h_cP);
 85      normalize(_h_c );
 86    }
 87
 88    /// @}
 89
 90
 91    /// @name Histograms
 92    /// @{
 93    Histo1DPtr _h_cP,_h_c;
 94    /// @}
 95
 96
 97  };
 98
 99
100  RIVET_DECLARE_PLUGIN(BABAR_2011_I892421);
101
102}